FR3071023A1 - PIVOT FOR SMOOTH BEARING - Google Patents

Abstract

The invention relates to a pivot (58) for an epicyclic planetary bearing, comprising an annular wall (50) delimiting an axial passage (51) and comprising a first (52c) and a second (54c) annular groove opening axially in directions. opposed (L1, L2) and each delimited by two inner annular branches (52a, 54a) and outer (52b, 54b) formed at the axial ends of the annular wall (50). According to the invention, the recesses (60) are made in at least one bottom wall (52d, 54d) of one of the annular grooves (52c, 54c).

Description

PIVOT FOR SMOOTH BEARING

FIELD [001] The present invention relates to a pivot for plain bearing and more particularly a pivot intended to be integrated in a planetary gear train of a turbomachine such as a turbojet or a turboprop.

BACKGROUND Conventionally, a planetary gear train comprises planet gears engaged with an outer ring gear and a central gear. The planet gears are carried by a planet carrier and mounted to rotate freely on pivots. Such a planetary gear train can be used in particular for the transmission of power from a motor shaft such as the shaft of a low pressure compressor connected to the central pinion, to a fan wheel connected to the planet carrier.

Each pivot is formed by an annular wall defining an axial passage and comprising first and second annular grooves opening axially in opposite directions. Each groove is delimited by two internal and external coaxial annular branches formed at the axial ends of the annular wall. The internal and external branches of each groove provide flexibility at the axial ends of the pivot, thereby limiting the deformation of the pivot and thus ensuring good radial alignment of the teeth of the planet gears with the central pinion and the external crown. However, it can be seen that this type of pivot is not yet optimal since it contributes significantly to the total mass of the planetary gear.

SUMMARY OF THE INVENTION The present invention relates first of all to a pivot for a plain bearing of planetary gear, comprising an annular wall delimiting an axial passage and comprising a first and a second annular grooves opening axially in opposite directions and each delimited by two internal and external coaxial annular branches formed at the axial ends of the annular wall, characterized in that recesses are made in at least one bottom wall of one of the annular grooves.

The recesses are made in a massive zone of the pivot, which makes it possible to reduce the mass of the pivot. In addition, this area has the advantage of being subject to few mechanical stresses in operation. These recesses can be made by drilling on an existing pivot in accordance with the prior art, which turns out to be simple and quick to produce.

According to another characteristic of the invention, the recesses are openings opening at a first end in the first annular groove and at a second opposite end in the second annular groove.

The orifices can be regularly distributed around the axial passage. They can also be distributed uniformly over a given angular sector around the axial passage, the angular zone devoid of orifices as mentioned above can then accommodate one or more conduits for the passage of lubricating oil extending from the axial passage to 'to an outer surface of the pivot.

The orifices can be substantially rectilinear and their axes can advantageously be inclined relative to the axis of the axial passage, preferably at an angle between 0 ° and 30 °. This latter configuration makes it possible to reduce the mass while retaining good mechanical rigidity at the pivot.

The invention also relates to a planetary gear train of a gas turbomachine for aircraft, comprising an outer ring and planet gears engaged with the central pinion and with the outer ring and each mounted free to rotate on a satellite carrier, the satellite pinions which can each rotate around a satellite axis via a pivot as described above.

[010] Also, the invention relates to a gas turbomachine for aircraft comprising a gear train whose central pinion surrounds and is rotatably integral with a shaft of the compressor of the turbomachine. More specifically, the outer ring can be secured to a static annular housing or ferrule of the low pressure compressor. In this configuration, the planetary gear train forms a reduction gear since the speed of rotation of the planet carrier is lower than that of the central pinion.

[011] Obviously, the invention is also applicable to planetary gear trains such as for example planetary gear trains in which the outer ring is also movable in rotation.

The invention is also applicable to a planetary gear train in which the planet carrier is fixed and the outer ring is movable. This type of assembly is also called planetary reduction gear.

The invention will be better understood and other details, characteristics and advantages of the invention will appear on reading the following description given by way of nonlimiting example with reference to the accompanying drawings.

BRIEF DESCRIPTION OF THE FIGURES FIG. 1 is a schematic perspective view of a turbomachine according to the known technique;

Figure 2 is a schematic sectional view of a planetary gear train for use in a turbomachine according to Figure 1;

Figure 3 is a schematic sectional view of a satellite pinion and the satellite carrier of Figure 2;

Figure 4 is a schematic sectional view of a pivot around which rotates a planet gear;

Figures 5A, 5B, 5C, 5C and 5D are schematic views of a first embodiment of the invention;

Figure 6 is a schematic axial view of a pivot according to a second embodiment of the invention;

FIG. 7 is a schematic side view of the pivot of FIG. 6.

DETAILED DESCRIPTION [014] First of all, reference is made to FIG. 1 which represents a schematic view of a turbomachine 10 according to the known technique comprising from upstream to downstream a fan wheel 12 whose rotation induces an acceleration of air in an annular secondary air stream 14 (air flow B) successively surrounding an annular primary air stream 16 (air flow A) flowing in a low pressure compressor 18, a high pressure compressor 20, a annular combustion chamber 22, a high pressure turbine 24 and a low pressure turbine 26. Conventionally, the low pressure turbine 26 rotates the rotor 30 of the low pressure compressor which is connected to the blower wheel 12. However, to limit the speed of rotation of the fan wheel 12 relative to the speed of rotation of the rotor 30 of the low pressure compressor 18, it is known to mount a planetary gear train 32 radially to the within the low pressure compressor 18, the epicyclic gear 32 then being qualified reducer because of its function of rotational speed reduction.

Such a gear train 32 comprises planet gears 34 engaged with an internal sun gear 36 or central pinion and with an external sun gear 38 or outer ring, the internal sun gear 36 and external 38 being coaxial with the axis X of the turbomachine. Each satellite pinion 34 is mounted to rotate freely around a pivot 40 and the pivots 40 are integral with a planet carrier 42. In an epicyclic reduction gear, the central pinion 36 is integral in rotation with the shaft 30 of the low compressor pressure 18 which forms an inlet to the gear train, the planet carrier 42 secured to the fan wheel 12 forms an outlet for reducing the speed of the planetary gear train and the outer ring 38 is made integral to a casing 44 of the turbomachine internally delimiting an annular zone in which the gear train is mounted.

The invention which will be described later thus applies not only to a gear train 32 of the reducing type but also to a gear train in which the outer ring 38 is connected in rotation to a second fan wheel , the outer ring 38 and the planet carrier being configured / dimensioned to rotate in opposite directions.

[017] Figure 3 shows a sectional view of a pivot 40 around which is engaged a pinion gear 34 so as to form a smooth bearing, the peripheral teeth 46 of the pinion 34 being shown in engagement with the peripheral teeth 48 of the central pinion 36 but not with the outer ring which is not shown in this figure.

As is clearly visible in this figure and more specifically in Figure 4, the pivot 40 includes an annular wall 50 which delimits radially inward an axial passage 51 extending along the axis X1 of the pivot. This annular wall 50 comprises a first annular end part 52 and a second annular end part 54 opposite the first part 52. The first annular part 52 and the second annular part 54 are separated by an intermediate annular part 56 or intermediate . The first annular part 52 comprises two radially internal 52a and external 52b annular branches 52b delimiting a first groove 52c or annular groove opening in a first direction L1 from the axial direction X1. Likewise, the second annular part 54 comprises two coaxial radially internal 54a and external 54b annular branches delimiting a second groove 54c or annular groove opening in a second direction L2 from the axial direction X1. In FIG. 4, the radially internal branch 52a of the first annular part 52 and the radially internal branch 54a of the second annular part 54 extend axially over a distance greater, respectively, than the radially external branch 52b of the first annular part 52 and to the radially external branch 54b of the second annular part 54. The radially internal branches 52a, 54a and external 52b, 54b of each of the first annular part 52 and second annular part 54 provide flexibility to the pivot in operation. However, it was noted that the mass of the pivot 40 was still too large and that an attempt was made to reduce it.

To this end, it is proposed, in a first embodiment of a pivot 58, to make recesses 60 of material in the intermediate annular part 56 which corresponds to the most massive part of the pivot 58. These recesses 60 are, in the various embodiments, orifices produced, for example by drilling, through the bottom wall 52d of the first and second grooves 52, 54. Each orifice 60 thus opens out at a first end in the first groove 52c and at a second end in the second groove 54c. In this embodiment, the orifices 60 are substantially rectilinear and substantially parallel to the axis X1 of the axial passage. As can be seen in FIGS. 5B to 5D, the orifices 60 are advantageously regularly distributed over an angular sector less than 360 ° in order to prevent the bores 60 from passing through oil circulation lines 62 used in particular for lubrication of the previously described plain bearing.

In another embodiment of the invention shown in Figure 6 and better visible in Figure 7, the pivot 64 the holes 66 are here inclined relative to the axis X1 of the axial passage at an angle between 0 ° and 30 ° [021] In other embodiments not shown, the pivot could include material recesses having the shape of orifices such as blind holes which however prove to be more difficult and costly to produce. First holes could be formed for example in the bottom wall of the first groove and extend axially or be inclined as in the second embodiment shown in Figures 6 and 10 7. Second holes could be formed in the bottom wall the second groove and extend axially or be inclined as in the second embodiment shown in Figures 6 and 7. The first and second holes can also be arranged alternately circumferentially around the axis of the pivot.

Claims (8)

1. Pivot (58, 64) for a plain bearing of a planetary gear train, comprising an annular wall (50) delimiting an axial passage (51) and comprising a first (52c) and a second (54c) annular grooves opening axially in opposite directions (L1, L2) and each delimited by two annular coaxial internal (52a, 54a) and external (52b, 54b) branches formed at the axial ends of the annular wall (50), characterized in that recesses (60, 66) are made in at least one bottom wall (52d, 54d) of one of the annular grooves (52c, 54c). 2. Pivot (58, 64) according to claim 1, in which the recesses (60, 66) are orifices opening at a first end in the first annular groove (52c) and at a second opposite end in the second annular groove ( 54c). 3. Pivot according to claim 2, wherein the orifices are regularly distributed around the axial passage (51). 4. Pivot according to claim 2 or 3, wherein the orifices (60, 66) are substantially rectilinear. 5. Pivot according to claim 4, wherein the orifices (66) are inclined relative to the axis (X1) of the axial passage (51), preferably at an angle between 0 ° and 30 °. 6. Planetary gear train of a gas turbomachine for aircraft, comprising an outer ring (38) and planet gears (34) engaged with the central pinion (36) and with the outer ring (38) and each mounted to rotate freely on a planet carrier (42), the planet gears (34) each being able to rotate about a satellite axis (X1) by means of a pivot (58, 64) according to any one of claims 1 to 6. 7. A gas turbomachine for an aircraft comprising a gear train according to claim 6, the central pinion (36) of which surrounds and is rotatably connected to a shaft (30) of the compressor of the turbomachine. 8. A turbomachine according to claim 7, in which the outer ring (38) is integral with a casing (44) or with a static annular shroud of the low pressure compressor (28).